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Red cedar encroachment threatens grasslands

Foot by foot, acre by acre, a green scourge is threatening Oklahoma’s rangeland.

Sam Fuhlendorf, Oklahoma State University natural resource ecology and management regents professor and Groendyke Chair for wildlife conservation, calls it “the green glacier,” the persistent encroachment of eastern red cedar across “some of the best grassland in the world.”

Fuhlendorf, speaking at the recent Rural Economic Outlook Conference on the OSU campus in Stillwater, said spread of the eastern red cedar can transform highly productive rangeland into limited production quickly. The infestation extends well into Texas and across much of the Southwest, creating significant economic losses.

The trees rapidly shade out valuable vegetation. “Nothing grows under red cedar canopies,” Fuhlendorf says. That means loss of forage for cattle and other livestock as well as wildlife. The infestation also turns productive rangeland into woodlands, removing habitat for the endangered lesser prairie chicken as well as bobwhite quail.

The invasive evergreen species affects the water profile, especially in winter as it continues to pull moisture from the soil. It also increases potential for wildfire and may create human health problems for those with allergic reactions and asthma.

Fuhlendorf said the trees grow as much as one foot per year, in both height and diameter.

He commented on two research efforts, one at the experiment station in Sonora, Texas, and the other in Stillwater. In some studies, tree cover changed from 10 percent to more than 50 percent over a 20-year period and production changed from an economic return to zero return.

Of two research sites in Stillwater, one remains highly productive because of management practices. The key, he said, is to apply proper management to vulnerable areas before red cedar becomes established. Heavy grazing and prescribed burns are two possible management options. He said burning once in ten years may allow landowners to maintain productivity for 150 years. A combination of fire and grazing is best, he said.

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“With highly productive grassland, producers can burn and graze more effectively. Most vegetation is highly adaptive to fire. Eastern red cedar and junipers are not. A lack of fire encourages spread.”

He said goats might be a better choice for grazing than cattle to slow down or stop red cedar encroachment.

He recommends managers burn patches instead of entire pastures. “Cattle will graze new growth in the burned areas. The burned areas also accumulate more fuel to support fire.”

Control options

Fuhlendorf says several options have been tried to manage red cedar, including finding a use for the trees. “But we have too many acres (infested). Production of cedar oil was an option but not enough demand exists. We have no viable options to use the trees.”

Other management practices include herbicides, cutting and a combination of burning, herbicide application and removal of trees.

Herbicides, he said, are expensive and require top-kill, no green above ground. “Cutting the trees does not offer a long-term solution.”

Burning and controlled grazing offer the best opportunities to manage the “green glacier,” he says. “Most grasslands in Oklahoma have some red cedar problems.”

Burning comes with risks, including damage to private property, human safety, soil erosion and smoke, which can create problems on roadways.

Fuhlendorf said cooperation between landowners, communities and various agencies may provide the key for successful prescribed burns. He said Osage County, Okla., and the Flint Hills in Kansas have “established a fire culture that is useful to land management. Land cooperatives where landowners work together to maintain grassland productivity using fire and other options offer potential.” He said about 20 such cooperatives are active in the state.

Fuhlendorf said the natural vegetation resource in Oklahoma and other Southwestern states is too valuable to allow red cedar to destroy productivity. Encroachment can change productivity of rangeland from producing vegetation capable of supporting four cows per acre to supporting one-sixth of a cow per acre. Economic return may drop to nothing.